3, 3&#39;-(2, 2, 4, 4-tetraalkylcyclobutane-1, 3-dioxy) bispropionic acid



United States Patent 3,157,696 3,3'-(2,2,4,4-TETIRAALKYLCYCLOBUTANE-1,3-DEGXQBISPRGlIfiNIC ACID Edward U. Eiam and James C. Martin, Kingsport,Tenn, assignors to Eastman Kodak Company, Rochester, N.Y., a corporationof New Jersey No Drawing. Original application Sept. 22, 1960, Ser. No.57,638, now Patent No. 3,099,679, dated July 30, 1963. Divided and thisapplication Oct. 22, 1962, Ser. N0-

2 Claims. or. 260-514) I NCCHzCHzOC COCHZOHZCN 3,3(2,2,4,4-tetraa1kylcyclobutane-l,3-dioxy) bispropionitrile and C OCHsCHrCN 2,2,4,4-tetraa1ky1-3- (2-cyanoethoxy) cyclobuantol where R R Rand R are lower alkyl groups contain ing from one to four carbon atoms,such as methyl, ethyl, propyl, isopropyl, butyl and isobutyl. R R R andR can be identical alkyl groups or any combination of such alkyl groups.

The nitrile compounds of the invention are prepared by reactingacrylonitrile in the presence of a basic catalyst with a2,2,4,4-tetraalkyl-1,3-cyclobutanediol of the general formula:

(III) R where R R R and R are as defined above. This glycol can beprepared by condensing two molecules of dimethyl ketene to obtain the2,2,4,4-tetramethyl-1,3-cyclobutanedione and then hydrogenating thelatter compound, as described in the patent to Hasek et al., US.2,936,324.

Tetraalkylcyclobutanediols of the above structure exist in at least two,and in many cases several, stereoisomeric forms. For the purposes of thepresent invention no distinction is made between these stereoisomericforms.

Any one of them or a mixture of the stereoisomers of any one glycol canbe used for preparing the compounds of the invention. However, differentstereoisomeric compounds of the invention will have somewhat differentphysical properties which will make a particular one or a particularcombination of ditferent stereoisomers more desirable than others forparticular applications.

The nitriles of our invention are useful as solvents for many organicmaterials, e.g., for various polymers. They ice are also useful asplasticizers for various synthetic resins, e.g., poly(vinyl chloride).They are particularly useful as intermediates for preparing differentvaluable compounds including certain novel compounds of our invention,such as the corresponding amines and carboxylic acids, from which usefulpolymeric materials can be prepared, as we will describe more fullyhereinafter.

The nitriles of the invention are prepared by reacting acrylonitrilewith a 2,2,4,4-tetraalkylcyclobutane-1,3-diol. The reaction can becarried out over a considerable temperature range. Temperatures fromabout 0 C. to C. are suitable, although temperatures somewhat below orabove this range can be used. At the lower temperatures thetetraalkylcyclobutanediols react sluggishly; at the higher temperaturesthe condensation reaction tends to be reversed and polymerization of theacrylonitrile gives tarry materials which are hard to separate from thedesired products. In general, reaction temperatures between 50 C. and 90C. will give the best results. This is the preferred temperature range.

It is usually convenient to carry out the reaction in the presence of asolvent, particularly for those tetraalkylcyclobutanediols which aresolids at temperatures below about 50 C. Any solvent which does notreact with acrylonitrile or destroy the catalyst under the reactionconditions can be used. Suitable solvents include aliphatic nitrilessuch as acetonitrile, propionitrile or isobutyronitrile,dimethylformamide, and, at lower temperatures, tert-butyl alcohol.

In general, any basic material will function as a catalyst for thecyanoethylation reaction. Examples of suitable catalysts include sodium,sodium and potassium alkoxides, hydroxides and cyanides; quaternaryammonium hydroxides such as benzyltrimethylammonium hydroxide (TritonB); and strongly basic tertiary amines such as triethylenediamine.

The choice of mole ratio of acrylonitrile to diol in the reactionmixture will depend on whether it is desired to obtain the monoor thedi-cyanoethylation product or a mixture thereof. A mole ratio of 1:1 orlower can be used for obtaining the mono-cyanoethylation product. If itis desired to prepare the dinitrile in high purity, the mole ratioshould be 2:1 or higher, e.g. 4:1. The order of addition of thereactants is not critical. In general, however, it is preferred to addacrylonitrile to a solution of the catalyst (if used) in the glycol andsolvent.

The following examples illustrate preparation of novel dinitriles of theinvention.

Example 1 A mixture of 526 g. (4 moles) of 2,2,4,4-tetramethyl-1,3-cyclobutanediol, 5 ml. of Triton B, and 450 ml. of acetonitrile wasplaced in a 3-liter, 3-necked fiaslr fitted with a sealed stirrer, areflux condenser, and a Y tube which contained a thermocouple well and adropping funnel. Eight hundred grams (15.1 moles) of acrylonitrile wasthen added over a period of about 15 minutes. The temperature rose to 75C. during the addition. The mixture was refluxed for about 1.5 hoursafter addition was complete, then allowed to stand overnight at roomtemperature. The crude product was acidified with a little hydrochloricacid, and the excess acrylonitrile was stripped off by distillation to abase temperature of C. at 10 mm. The residue was distilled through ashort packed column to give, after removal of 61.7 g. of lowboiler, thefollowing fractions: (1) -75 (2.5 mm.),

54.7 g.; (2) (2.5 mm.), 173 (2.0 mm.), Ml.

43-59 C., 179g.; (3) 173-6 (2.0 mm.), Ml. 47-57 C., 548 g.; and (4)17690 C. (2.0-2.5 min), 126.3 g. The residue weighed 50 g. The totalyield of mixed isomers of3,3'-(2,2,4,4-tetramethylocyclobutane-1,3-dioxy)bispropionitrile(fractions 14) was 90.8%.

Analysis.-Calcd. for C H N O C, 67.1; H, 8.80; N, 11.2. Found: Fraction1, N, 10.8; fraction 2, N, 11.3; fraction 3, C, 67.2; H, 8.50; N, 11.1;fraction 4, N, 11.4.

Example 2 The procedure of Example 1 was followed except that the dioland acrylonitrile were mixed in the reaction flask and the catalyst wasadded dropwise to the stirred mix ture. A sudden exothermic reaction,which carried the temperature to 90-95" 0, took place. The residuecrystallized after neutralization of catalyst and distillation of theexcess acrylonitrile and solvent, giving a quantitative yield of crudedinitrile.

Example 3 The procedure of Example 1 was repeated with2,4-dibutyl-2,4-diethyl-1,3-cyc1obutanediol. The yield of 3,3- (2,4dibutyl-2,4-diethylcyclobutane-l,3-dioxy)bispropionitrile was 85%.

Example 4 The procedure of Example 1 was followed, except thattort-butyl alcohol was substituted for acetonitrile as the solvent,sodium tert-butoxide was used as the catalyst,

and the reaction temperature was held below 40 C.

3,3'-(2,2,4,4-tetramethylcyclobutane-l,3-dioxy)bispropionitrile wasobtained in 80% yield.

The following example describes the preparation of 3 (2cyanoethoxy)-2,2,4,4-tetramethylcyclobutanol by monocyanoethylation oftetramethylcyclobutanediol. Other tetraalkylcyclobutanediols undergo ananalogous reaction.

Example 5 A mixture of 288 g. (2 moles) of 2,2,4,4-tetramethyl-1,3-cyclobutanediol, 500 ml. of acetonitrile, and 5 ml. of Triton B wasplaced in a 2-1. flask which was fitted with a sealed stirrer, a refluxcondenser, a thermowell, and a dropping funnel. Acrylonitrile (212 g., 4moles) was then added gradually with stirring. A mild exothermicreaction occurred and the temperature of the mixture rose to 64 C. Afterthe exothermic reaction Was over, the mixture was refluxed and stirredfor two hours, then acidified with ml. of concentrated hydrochloric acidand distilled. The yield of 3-(2-cyanoethoxy)-2,2,4,4-tetramethylcyclobutanol (mixed cis and trans isomers) boiling from140152 C. at 4.5 mm. was 120 g.

Analysis.-Calcd. for C H NO C, 67.0; H, 9.64, N, 7.10. Found (14452/4.5mm.) fraction: C, 66.4; H, 9.67; N, 7.47.

We have indicated that the nitriles of our invention are useful aschemical intermediates. Thus, the 3,3'-( 2,2, 1,4-tetraalkylcyclobutane-1,3-dioxy)bispropionitriles can be hydrolyzed tothe corresponding bispropionic acids. The acids are also novel compoundsof our invention; They are useful in the same applications as otherdibasic acids, i.e., for preparing polyesters, polyamides, etc. Thefollowing example describes preparation of a typical dibasic acid of ourinvention:

Example 6 One hundred seventy-four grams of3,3'-(2,2,4,4-tetramethylcyclobutane-l,3-dioxy)bispropionitrile wasadded slowly, with stirring, to 370 g. of concentrated hydrochloric acidwhich had been preheated to 50 C. The temperature rose during theaddition to 95 C., then fell slowly to 50 C., Where it was maintainedfor approximately 39 hours. The reaction mixture was then cooled,diluted with water, and extracted thoroughly with ether. The etherextract was washed with 20% sodium hydroxide until the washings werebasic. The aqueous alkaline solution, after washing with fresh ether,was filtered from a small amount of suspended solid, acidified withconcentrated hydrochloric acid, and extracted thoroughly with ether. Theether extracts were washed with water, dried over Drierite, filtered,and evaporated to dryness. The

Example 7 3,3 (2,2,4,4 tetramethylcyclobutane-1,3-dioxy)bispropionicacid was esterified with isobutyl alcohol in the usual manner, byrefluxing it with an excess of isobutyl alcohol in the presence of alittle p-toluene sulfonic acid. The resulting diisobutyl ester of3,3-(2,2,4,4-tetramethylcyclobutane-1,3-dioxy)bispropionic acid was aclear, slightly viscous liquid which showed excellent compatibility withcellulose acetate, cellulose acetate-butyrate, and poly(vinyl chloride)resins. The cellulosic and poly (vinyl chloride) resins plasticized withthis ester showed excellent clarity, low color, and good low temperatureproperties. This ester may also be made by saturating an isobutylalcohol solution of3,3-(2,2,4,4-tetramcthylcyclobutane-1,3-dioxy)bispropionitrile withanhydrous hydrogen chloride, refluxing several hours, filtering,washing, and distilling.

Example 7 illustrates preparation of the novel diisobutyl alcohol esterof our acid of Example 6 and indicates the advantages of the ester as aplasticizer for cellulosics and poly(vinyl chloride). Esters preparedfrom alkyl alcohols having two to eight, preferably four to six, carbonatoms are generally the best plasticizers. In comparison with certainother cycloalkyl dihydroxy alcohol esters, the various esters of ourinvention will be superior in one or more of the following properties:good compatibility with cellulose esters and poly(vinyl chloride), theresulting compositions having good lowtemperature impact strength; goodresistance to oxidation, resulting in improved color in the moldedproducts plasticized with our ester; somewhat bettertemperatureviscosity characteristics and improved stability to oxidationin synthetic lubricants. The improved resistance to oxidation isespecially noticeable in the derivatives of the highertetraalkylcyclobutanediols, such as those of 2,2,4,4-tetraethyl-1,3-cyclobutanediol.

Another important class of derivatives of our novel nitriles comprisesthe diamines and aminoalcohols which are prepared by hydrogenating thenitriles. Thus, the novel compositions of our invention include3,3-(2,2,4,4- tetraalkylcyclobutane-l,3-dioxy)bispropylamines and 2,2,4,4-tetraalltyl-3-(Z-cyanoethoxy)cyclobutanols which can be prepared byhydrogenation of the nitriles of Formulas I and II above. The reactionis represented by the following equation:

(IV) R1 R2 Noomcn.

OOHgCHiCHzNH:

H C H HO /C\ OCHQCHGCHZNHQ CHsCHzCHzNIlg 33 R4 where R, R R and R arelower alkyl groups containing from one to four carbon atoms, such asmethyl, ethyl, propyl, isobutyl, and n-butyl.

Hydrogenation of the 3,3-(2,2,4,4-tetraalkylcyclobutane-l,3-dioxy)bispropionitriles can be carried out over a wide range oftemperatures and pressures. However, it is preferable to operate at aslow a temperature as possiblein order to avoid hydrogenolysis of theether linkage, giving propylamine and tetrmethylcyclobutanediol or theaminoalcohol (in the event that the latter compound is not desired) Thepreferred temperature range for the hydrogenation is between 50 C. and150 C., although lower and higher temperatures from O C. or lower to 200C. or higher will give some of the desired products. The partialpressure of hydrogen in the reaction mixture is also not critical, andwill depend primarily upon the amount and type of hydrogenation catalystemployed. In general, pressures between 50 and 5,000 p.s.i. can be used.The preferred pressure range, for rapid reaction without excessiveequipment costs, is between 1,000 and 3,000 p.s.i.

Any of the common hydrogenation catalysts, such as Raney cobalt, nickel,or iron; noble metals such as plati nurn, palladium, rhodium, orruthenium; or their oxides or easily reducible salts can be used in theprocess of the invention. The active catalyst can be supported on aninert carrier such as kieselguhr, carbon, alumina, calcium carbonate,barium sulfate, or the like, either in powder or pellet form, ifdesired.

It is usually advantageous, but not essential, to carry out thehydrogenation in the presence of ammonia, in order to inhibit theformation of secondary amines and polymers. The use of a solvent is alsoadvantageous. For this purpose, any solvent which is inert under thehydrogenation conditions, and which does not react with the reductionproducts can be used. Methyl and ethyl alcohol are examples of suitablesolvents.

The following examples describe the preparation of our novel amines:

Example 8 A mixture of 380 g. (1.52 moles) of3,3-(2,2,4,4-tetramethylcyclobutane-1,3-dioxy)bispropionitrile, 400 ml.of methanol, and 25 g. of alcohol-washed Raney nickel was placed in a1780-m1. stainless steel autoclave. The autoclave was sealed and 300 ml.of anhydrous ammonia was added from a blowcase. Hydrogen was then addedto raise the pressure to 1500 p.s.i., the autoclave was heated to 125C., and the hydrogenation was completed at 2500 p.s.i. total pressure (6hr.). The product was filtered and distilled through a l-in. x 8-in.packed column to give, after removal of solvent and some low-boilers,fractions boiling from (1) 140-145 C. (5-4 mm.), 11 1.4701, 44.3 g.; (2)145 C. (4-4.5 mm.), 11 1.4680, 113.6 g., and (3) 145-53 C. (4.5-5 mm.),n 1.4662, 137.4 g. Higher boiling material weighed 49.1 g. The yield ofcrude 3,3-(2,2,4,4-tetramethylcyclobutane-1,3-dioxy)bis propylamine(fractions 2 and 3) was 251.0 g. (64%).

Analysis.-Calcd. for C I-1 N 0 Neut. equiv., 129. Found: Fraction 1,215; fraction 2, 144; fraction 3, 131.

Fractions 1, 2, and 3 above were combined and carefully refractionatedto give fractions boiling from (1) 109.5-17.0 C. (1.6 mm.), 28 ml.; (2)116-123 C. (2.0- 1.8 mm.), 25 ml. (solidified on cooling); (3) 123-36(1.8 mm.), 40 ml., and (4) 136-151 (1.8-5.0 mm.), 11 1.4660, 160 ml.

6 A.rzalysis.C-alcd. for C l-i NO (aminoalcohol): Neut. equiv. 201.Calcd. for C I-1 N 0 (diamine): Neut. equiv. 129. Found: Fraction 1,207; fraction 2, 199; fraction 4, 129.

The above analysis shows that fractions 1 and 2 obtained by carefulrefractionation in Example 8 were essentially pure3-(2-cyanoethoxy)-2,2,4,4-tetramethylcyclobutanol, and fraction 4 waspure 3,3'-(2,2,4,4-tetraniethylcyclobutane-1,4-dioxy) bispropylarnine.

Example 9 Example 10 3,3 (2,4 dibutyl 2,4 diethylcyclobutane 1,3dioxy)bispropionitrile was hydrogenated as described in Example 8 togive 3,3-(2,4-dibutyl-2,4-diethylcyclobutanel,3-dioxy)bispropylamine in50% yield.

The 3,3-(2,2,4,4 -tetraalkylcyclobutane-1,3-dioxy)bispropylamines areparticularly useful as intermediates for the preparation of highmolecular weight polyamides. The following example demonstrates theutility of our novel amines for preparing valuable polyamides.

Example 11 A salt was prepared by reacting equimolar amounts of3,3-(2,2,4,4 tetramethylcyclobutane 1,3 dioxy)bispropylamine andterephthalic acid. A low molecular weight prepolyrner was prepared byheating this salt for several hours in p-cresol solution. The p-cresolwas then removed, and the polymerization completed in vacuo at a finaltemperature of 280 C. The resulting polyamide had an inherent viscosityof 0.4 and a melting range of 178-82" C. This polymer formed a flexible,transparent film.

Although the invention has been described in considerable detail withreference to certain preferred embodiments thereof, it will beunderstood that certain modifications can be eliected without departingfrom the scope of the invention as described hereinabove and as definedin the appended claims.

We claim:

1. A 3,3'-(2,2,4,4-tetraalkylcyclobutane-1,3-dioxy)bispropionic acid ofwhich the alkyl groups contain one to four carbon atoms.

2. 3,3 (2,2,4,4 tetramethylcyclobutane 1,3 dioxy) bispropionic acid.

References Cited in the file of this patent Stimson et al.: J. Org.Chem, vol. 19' (1954) page 1047.

Mousseron et al.: Chem. Abst., vol. 42, page 1901c (1948).

1. A 3,3''-(2,2,4,4-TETRAALKYLCYCLOBUTANE-1,3-DIOXY) BISPROPIONIC ACIDOF WHICH THE ALKYL GROUPS CONTAIN ONE TO FOUR CARBON ATOMS.